We consider the problem of finding the best approximation to $\bar{ z}$ in the Bergman Space $A^{ 2}(\Omega)$. We show that this best approximation is the derivative of the solution to the Dirichlet problem on $\partial\Omega$ with data $\left|z\right|^{ 2}$ and give examples of domains where the best approximation is a polynomial, or a rational function. Finally, we obtain the "isoperimetric sandwich" for $dist(\overline{ z},\Omega)$ that yields the celebrated St. Venant inequality for torsional rigidity.
Categories: math.CV